To make competitive optical computers and photonic switches, optical devices are required that perform functions that are similar to the functions performed by electronic devices in electronic systems. By using optoelectronic devices, such as the quantum well self electro-optic effect devices (SEEDs) disclosed in U.S. Re. Pat. No. 32,893 issued to D. A. B. Miller on Mar. 21, 1989, many such corresponding functions can be achieved. The symmetric SEEDs (S-SEEDs) disclosed in U.S. Pat. No. 4,754,132 issued to H. S. Hinton et al. on June 28, 1988 have been shown to operate as set-reset latches, differential logic gates, or optical tri-state logic devices (U.S. Pat. No. 4,800,262 issued to A. L. Lentine on Jan. 24, 1989). More recently, S-SEEDs have been applied as logic gates capable of implementing any boolean logic function in a single combinational circuit with a single clock cycle of delay (allowed U.S. patent application Ser. Nos. 07/399,638 and 07/399,730 of A. L. Lentine et al.). This is important because it avoids the optical cascading otherwise needed to perform more complex logic functions; the approach is lacking, however, in that there is no apparent way to implement sequential circuits, such as shift registers, counters, multiplexers and demultiplexers.
Allowed U.S. patent application Ser. No. 07/283,336 of H. S. Hinton et al. discloses one known sequential optical circuit apparatus comprising optically cascaded S-SEEDs in an integrated structure; while the monolithic structure eliminates the need for the bulk optics of free space optically interconnected subsystems, the structure is complex, and adds capacitance thereby reducing system speed. Because the devices are optically cascaded, it is not possible in some applications to use short pulses to rapidly switch the devices because of saturation of the first device of a cascaded pair. In view of the foregoing, a recognized deficiency in the art is the lack of an apparatus for implementing optical sequential logic without requiring optical cascading.